Conventional liquid rocket engines like the Saturn V's S-1C stage F-1, the Space Shuttle's SSME, the Delta 1-3 RS-27, Delta 4's RS-68 and RL-10, typically used in upper stages, are based on a convergent-divergent/Rao nozzle configuration for simplicity and performance. Their performance is traditionally measured in terms of specific impulse (Isp) and thrust-to-weight ratio (T/We). The performance of one or more of these types of engines can suffer from the atmospheric pressure effect on thrust. This results in a negative effect on Isp and weight due to linear integration of the combustion gas flow elements including power head, injector system, combustion chamber and nozzle.
Alternate configurations have been developed that use atmospheric pressure compensating nozzles that can, in some configurations, reduce the thrust and Isp penalty during atmospheric operation. These include the symmetric plug nozzle demonstrated by Pratt & Whitney Rocketdyne (PWR) and the 2-D PWR Aerospike that was to be used on the Lockheed Martin X-33. The alternate Expansion-Deflection nozzle concept also compensates for atmospheric pressure effects by permitting internal flow separation and pressure equalization. However, while these concepts can reduce thrust and Isp losses during the atmospheric flight phase, their weight and resulting lower T/We penalizes the overall mission performance measured by payload weight.
It is with respect to these and other considerations that the disclosure herein is presented.